I have the same info as posted above, a PCR test on blood for Mareks by RAL lab:I believe @Eggcessive has info on this. Kim, do you mind chiming in on how to test for Marek’s short of necropsy? Would you happen to also have the same info for Australia? Thank you!
https://www.vetdna.com/application/forms/aviansubmittalform.pdf
I think that University of GA also does this. The owner gets the materials for collecting a blood sample by trimming a toenail too short, and sends it back to the lab. It costs $20 for the kit, and you pay more for the test, I believe. @azygous has done this and may know exact prices, but the lab ought to be able to give you all of that info. Probably the best way to get a diagnosis is from a necropsy, where they can look at tissue and take samples for testing.